Integrated Drive Generators (IDGs) supply constant frequency alternating current (AC) electrical power to an aircraft. The IDG utilizes the constant speed drive as a highly reliable continuously variable transmission to convert a variable input speed provided by an aircraft's engine into a constant output speed for the IDG's integral AC generator. This integration of drive and generator provides a solution for delivering constant frequency electrical power to the aircraft.
Referring to FIG. 1, traditional IDGs 100 implement an exciter field winding 102 that is electrically energized by an exciter drive circuit 104 included in a generator control unit (GCU) 106. The conventional exciter drive circuit 104 typically includes a single semiconductor switch 110 implemented with a single flyback diode 108 to assist in dissipating energy flyback (e.g., voltage flyback) when the load (not shown) coupled to the IDG 100 is suddenly reduced or removed. A typical single switch exciter drive circuit as shown in FIG. 1, however, experiences gradual decay times when attempting to remove energy from the exciter field 102 during transient events caused by load disconnects, load reductions, and/or recovery from load faults, for example (see FIG. 2). As a result, the IDG 100 can experience a significant voltage overshoot if the exciter drive is unable to remove energy quickly enough from the exciter field after the IDG's load has been stepped from a heavy load to a very light load.